This invention relates to a surgical cutting instrument of the type employing rotary cutters. Instruments of this type are usable for various surgical procedures in various regions of the body, such as in the eye and knee. For example, the surgical cutting instruments may be inserted through a small opening into the knee joint and used for cutting the meniscus or other soft or hard material or tissue.
Generally, a surgical cutting instrument of this type includes an outer tube having a peripheral wall, an end wall, an opening in one or both of the peripheral wall and the end wall and a cutting edge defining at least a portion of the periphery of the opening. An inner cutting member, which may also be in the form of a tube, rotates or translates within the outer tube. The inner cutting member has a cutting edge that cooperates with the cutting edge of the outer tube for cutting material with a shearing action as the inner cutting member is moved relative to the outer tube. One surgical cutting instrument of this general type is shown and described in Johnson et al U.S. Pat. No. 4,274,414.
Another cutting instrument of this type is the whisker cutter. In this instrument, the outer tube has a plurality of small circular openings to adapt the instrument for cutting fine hair-like projections, such as synovial tissue, from within the knee. While the whisker construction is satisfactory for certain applications, it is not suitable for a broader range of applications. For example, the round edges of the circular small holes of the outer tube do not provide as good a scissors or shearing action as is desirable for some applications. In addition, the small holes also make the outer tube not particularly satisfactory for use as a curette.
Another type of inner cutter which has been suggested is a helical or auger cutter. For example, Banko U.S. Pat. No. 4,167,944 uses a helical cutter at the distal end of a device having a outer tube with a single circular opening. Staub, et al U.S. Pat. No. 4,014,342 uses an elongated helical cutter in conjunction with an outer tube having a single opening in the distal end thereof. Thimsen, et al U.S. Pat. No. 4,649,919 uses a helical cutter in combination with an outer sheath which is open at its distal end and proximally therefrom to form diametrically opposed tabs with inwardly extending lips. Pippin, U.S. Pat. No. 3,308,828 and Perrill U.S. Pat. No. 2,532,370 use helical cutters in conjunction with outer protective shields which do not have cutting edges or surfaces. These devices ten to become clogged with material removed from the patient's body, and/or are not effective or usable as a curette.
Notwithstanding a proliferation of known configurations for the outer tube and the inner cutting member, there are problems with poor cutting ability and inconsistent quality.